128 research outputs found
Detailed stellar population analysis of Early-Type galaxies with redshift to constrain their evolution
Una de las cuestiones básicas de la Astronomía moderna es cómo las galaxias
de las diferentes familias han evolucionado desde su formación. Una de estas
familias, las galaxias de tipos tempranos (ETGs, del inglés Early-Type Galaxy),
formadas por galaxias elípticas y lenticulares, que contienen la mayor parte de
la materia luminosa del Universo, ha sido profundamente estudiada durante
décadas. En esta tesis se propone esclarecer este tema, analizando las poblaciones
estelares de las ETGs masivas a trav´es del tiempo cósmico desde diferentes
puntos de vista. Para tal fin, explotamos las nuevas herramientas y métodos de
última generación, como el ajuste completo del espectro (full-spectral-fitting)
combinado con el análisis de los índices espectrales mediante los diagramas
índice-índice. La novedad de este trabajo est´a en el estudio detallado de las
poblaciones estelares, llevado a cabo galaxia por galaxia incluso a alto desplazamiento
al rojo. Este conjunto de observaciones y métodos utilizados, permite
acotar los diferentes escenarios propuestos para la formación y evolución de las
ETGs
Bridging the gap in the mass-size relation of compact galaxies with MaNGA
We present the analysis of the full MaNGA DR17 sample to characterize its
population of compact galaxies. We focus on galaxies that fill the stellar mass
(M) gap between compact elliptical galaxies (cEs; ) and compact massive galaxies
(CMGs; ). We study their
stellar populations and kinematics to reveal how their properties depend on
stellar mass. We select compact galaxies in the MaNGA DR17 sample according to
their effective radius () and stellar mass. 37 galaxies fulfill our
selection criteria in the bridging region between cEs and CMGs. We derive their
kinematics and stellar population parameters from the stacked spectra at
1~ using a full spectral fitting routine. We then classify the selected
compact galaxies in three main groups based on their stellar population
properties. One of the groups shows characteristics compatible with relic
galaxies, i.e. galaxies that have remained mostly unchanged since their early
formation epoch (). Another group shows more extended and continuous
star formation histories (SFHs). The third group shows a low star-forming rate
at initial times, which increases at around Gyr. We compare the derived
properties of the selected galaxies with those of previously studied compact
galaxies at different mass ranges. The selected galaxies successfully fill the
mass gap between cEs and CMGs. Their properties are compatible with the
assumption that the scaling relations of compact galaxies at different mass
ranges are related, although galaxies in the first group are clear outliers in
the fundamental plane, suggesting different formation mechanisms for this relic
population.Comment: 16 pages, 14 figures, 2 table
Prediction of Nonlinear Distortion in HTS Filters for CDMA Communicaction Systems
HTS materials are known to produce intermodulation and other nonlinear effects, and this may restrict their use in wireless communication systems. While significant efforts are being done to measure and characterize nonlinear properties of HTS materials, there are very few works that relate these properties to system parameters. In this work we attempt to bridge this gap by using harmonic balance algorithms to analyze the nonlinear performance of superconducting filters subject to the WCDMA signals specified by 3GPP for the UMTS wireless system. This is a first step to predict compliance with system parameters like adjacent channel leakage power ratio (ACLR) or error vector magnitude (EVM).Peer Reviewe
On the Stellar Kinematics and Mass of the Virgo Ultra-Diffuse Galaxy VCC 1287
Here, we present a kinematical analysis of the Virgo cluster ultra-diffuse
galaxy (UDG) VCC 1287 based on data taken with the Keck Cosmic Web Imager
(KCWI). We confirm VCC 1287's association both with the Virgo cluster and its
globular cluster (GC) system, measuring a recessional velocity of $1116 \pm 2\
\mathrm{km\ s^{-1}}19 \pm 6\
\mathrm{km\ s^{-1}}1.11^{+0.81}_{-0.81}
\times 10^{9} \ \mathrm{M_{\odot}}13^{+11}_{-11}$)
within the half light radius (4.4 kpc). This places VCC 1287 slightly above the
well established relation for normal galaxies, with a higher mass to light
ratio for its dynamical mass than normal galaxies. We use our dynamical mass,
and an estimate of GC system richness, to place VCC 1287 on the GC number --
dynamical mass relation, finding good agreement with a sample of normal
galaxies. Based on a total halo mass derived from GC counts, we then infer that
VCC 1287 likely resides in a cored or low concentration dark matter halo. Based
on the comparison of our measurements to predictions from simulations, we find
that strong stellar feedback and/or tidal effects are plausibly the dominant
mechanisms in the formation of VCC 1287. Finally, we compare our measurement of
the dynamical mass with those for other UDGs. These dynamical mass estimates
suggest relatively massive halos and a failed galaxy origin for at least some
UDGs.Comment: 13 pages, 10 figures with an additional 5 pages and 5 figures in
appendices. Accepted for publication in MNRAS. v2: with small updates from
publication formatting and a minor plotting fix for Fig. 1
Ultra deep sub-kpc view of nearby massive compact galaxies
Using Gemini North telescope ultra deep and high resolution (sub-kpc) K-band
adaptive optics imaging of a sample of 4 nearby (z~0.15) massive
(~10^{11}M_sun) compact (R<1.5 kpc) galaxies, we have explored the structural
properties of these rare objects with an unprecedented detail. Our surface
brightness profiles expand over 12 magnitudes in range allowing us to explore
the presence of any faint extended envelope on these objects down to stellar
mass densities ~10^{6} M_sun/kpc^{2} at radial distances of ~15 kpc. We find no
evidence for any extended faint tail altering the compactness of these
galaxies. Our objects are elongated, resembling visually S0 galaxies, and have
a central stellar mass density well above the stellar mass densities of objects
with similar stellar mass but normal size in the present universe. If these
massive compact objects will eventually transform into normal size galaxies,
the processes driving this size growth will have to migrate around
2-3x10^{10}M_sun stellar mass from their inner (R<1.7 kpc) region towards their
outskirts. Nearby massive compact galaxies share with high-z compact massive
galaxies not only their stellar mass, size and velocity dispersion but also the
shape of their profiles and the mean age of their stellar populations. This
makes these singular galaxies unique laboratories to explore the early stages
of the formation of massive galaxies.Comment: Accepted for publication in ApJ Letter. Version revised to match the
accepted versio
Keck Cosmic Web Imager (KCWI) Spectra of Globular Clusters and Ultra Compact Dwarfs in the Halo of M87
Using the Keck Cosmic Web Imager we obtain spectra of several globular
clusters (GCs), ultra compact dwarfs (UCDs) and the inner halo starlight of
M87, at a similar projected galactocentric radius of 5 kpc. This enables
us, for the first time, to apply the same stellar population analysis to the
GCs, UCDs and starlight consistently to derive ages, metallicities and
alpha-element abundances in M87. We find evidence for a dual stellar population
in the M87 halo light, i.e an 80\% component by mass which is old and
metal-rich and a 20\% component which is old but metal-poor. Two red GCs
share similar stellar populations to the halo light suggesting they may have
formed contemporaneously with the dominant halo component. Three UCDs, and one
blue GC, have similar stellar populations, with younger mean ages, lower
metallicities and near solar alpha-element abundances. Combined with literature
data, our findings are consistent with the scenario that UCDs are the remnant
nucleus of a stripped galaxy. We further investigate the discrepancy in the
literature for M87's kinematics at large radii, favouring a declining velocity
dispersion profile. This work has highlighted the need for more self-consistent
studies of galaxy halos.Comment: 12 pages, 10 figures, accepted for publication in MNRA
NGC 474 as viewed with KCWI: diagnosing a shell galaxy
We present new spectra obtained using Keck/KCWI and perform kinematics and
stellar population analyses of the shell galaxy NGC 474, from both the galaxy
centre and a region from the outer shell. We show that both regions have
similarly extended star formation histories although with different stellar
population properties. The central region of NGC 474 is dominated by
intermediate-aged stars (8.3 \pm 0.3 Gyr) with subsolar metallicity ([Z/H]=
-0.24 \pm 0.07 dex) while the observed shell region, which hosts a substantial
population of younger stars, has a mean luminosity-weighted age of 4.0 \pm 0.5
Gyr with solar metallicities ([Z/H]=-0.03 \pm 0.09 dex). Our results are
consistent with a scenario in which NGC 474 experienced a major to intermediate
merger with a log mass satellite galaxy at least \sim 2
Gyr ago which produced its shell system. This work shows that the direct
spectroscopic study of low-surface brightness stellar features, such as shells,
is now feasible and opens up a new window to understanding galaxy formation and
evolution.Comment: Accepted for publication in MNRAS, 6 pages, 5 figure
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